Method and apparatus for grinding a cylindrical surface



April 6, 1965 s. A. THOMPSON 3,176,440

METHOD AND APPARATUS FOR GRINDING A CYLINDRICAL SURFACE Filed May 24,1960 '7 Sheets-Sheet 1 IN V EN TOR.

EAFg L ATHOMPSON @267 jM ATTORA/B APril 5, 1955 E. A. THOMPSON 3,176,440

METHOD AND APPARATUS FOR GRINDING A CYLINDRICAL SURFACE Filed May 24,1960 7 Sheets-Sheet 2 F I Z INVENTOR. j EARL A. THOMPSQN W 6- AMM A ril6, 1965 A. THOMPSON 3,175,440

METHOD AND APPARATUS FOR GRINDING A CYLINDRICAL SURFACE Filed May 24,1960 7 Sheets-Sheet 3 IN VEN TOR.

EAR% A. THOMPSON ATTORNEY April 6, 1965 E. A. THOMPSON 3,176,440

METHOD AND APPARATUS FOR GRINDING A CYLINDRICAL SURFACE Filed May 24,1960 7 Sheets-Sheet 4 IN V EN TOR.

EAQ L A. THOM PSON A TTOR/VEV April 1965 E. A. THOMPSON 3,176,440

METHOD AND APPARATUS FOR GRINDING A CYLINDRICAL SURFACE Filed May 24,1960 7 Sheets-Sheet 5 2 i2; F i 66 a l 1 sgfi/ x V A 60 I i l Wit. r

fjys

IN V EN TOR.

EA L ATHOMPSON Mam ATTORNEY April 6, 1965 E. A. THOMPSON 3,

METHOD AND APPARATUS FOR GRINDING A CYLINDRICAL SURFACE Filed May 24,1960 '7 Sheets-Sheet 6 IN V EN TOR.

ATTORNEY April 6, 1965 E. A. THOMPSON METHOD AND APPARATUS FOR GRINDINGA CYLINDRICAL SURFACE '7 Sheets-Sheet 7 Filed May 24, 1960 INVENTOR.EARL ATHOMPSON ATTORNEY BY WK /Z surface on the wheel.

United States Patent 3,176,440 IVIETHOD AND APPARATUS FOR GRINDENG ACYLINDRICAL SURFACE Earl A. Thompson, 1300 Hilton Road, Ferndale, Mich.Filed May 24, 1960, Ser. No. 31,325 Claims. (Cl. 51-281) This inventionrelates to face grinding, and more particularly to a method andapparatus for grinding a curved surface on a workpiece and particularlyon a ledge projecting part or shoulder of a workpiece such as a valverocker arm of an automotive internal combustion engine.

In grinding such pieces by prior methods on known machines, one of themajor problems encountered is the difficulty of dressing the complementof the desired The surface dressed in the wheel must be very accuratelyformed as it will be accurately reflected on the work. To form such anaccurate surface on the wheel, a great deal of grit must often beremoved from the wheel during each dressing operation, and the dressingoperations must occur frequently because the grinding operation isconcentrated on a wheel area of limited width.

Accordingly, it is an object of the present invention to i provide amethod of grinding a cylindrical surface of small radius with a facegrinding wheel which may be dressed straight across with a minimum ofwastage. The term cylindrical surface as used herein includes a surfacedefined by the usual geometrical definition. That is, it is a surfacewhich is generated by moving an are or curved line (not necessarily acircular are) along a line transverse to its own plane. This line becomethe axis of the cylindrical surface. One characteristic of such acylindrical surface is that it can be developed or unrolled into aplane, as distinguished, for example, from a spherical surface whichcannot be so developed.

Another object of the present invention is to provide a method ofgrinding a cylindrical surface of comparatively small radius by means ofa straight face grinding wheel having an effective working widthconsiderably greater than the surface and in which the entire face isutilized during each grinding operation.

A further object of the present invention is to provide apparatus forautomatically accomplishing the grinding method of this invention.

A further object of the present invention is to provide ,amechanico-hydraulic drive system for powering and controlling theapparatus of this invention.

Further objects and advantages of the present invention will be apparentfrom the following detailed description, with reference to theaccompanying drawings in which like reference characters refer to thesame parts throughout the several views, and in which:

FIGURE 1 is a side view of the grinding machine of this invention;

FIGURE 2 is a plan view of the machine shown in FIG URE l;

FIGURE 3 is a semi-schematic plan view of a portion of the structureshown in FIGURE 2 on an enlarged :scale illustrating the manner in whichthe grinding wheel is moved to generate a cylindrical surface on aledged 1 FIGURE 6 is a sectional view taken along line ti-fi to fullyexpose its wide working area to the surface to be ground; and

FIGURE 7 is a view in schematic fashion of the mechanico-hydraulicmotivator of this invention.

While the disclosed grinding method and apparatus can readily be adaptedto grind a curved surface on a variety of workpieces in a variety ofenvironments, for purposes of illustration the invention will bedisclosed in relation to the grinding of a relatively small(approximately cylindrical surface on the valve stem-contacting end ofan automotive internal combustion engine rocker arm. Such a rocker arm Wis shown in FIGURES 3 and 4 fixedly positioned for the grindingoperation. The cylindrical surface 19 to be ground is on a ledge whichprojects laterally from an arm which projects move or less radially froma larger central cylindrical portion and is relatively inaccessible forgrinding by ordinary methods and apparatus. The reference character 12represents the axis of the cylindrical surface. This shows in thedrawings as the phantom line 12 in FIGS. 1 and 4 and the point 12 inFIG. 3. The latter is the trace of the axis in the plane of FIG. 3. Theworkpiece to be ground has a rough surface generally following thiscylindrical surface, which in the grinding operation, is accuratelyfinished by the Wheel.

Referring to FIG. 2, the rocker arm workpiece W is fixed during grindingon a rotary indexing table 14 having a plurality of workpiece grippingmechanisms 16 equidistantiy positioned in a circle near the periphery ofthe table. A single workpiece may be loaded upon and loosely received byone of the gripping mechanisms at a loading station 18, after which thetable is indexed to present the workpiece to a locating and grippingstation 2% where the workpiece is accurately positioned by means of arigid abutment 22 on a horizontally swinging arm 24 which also containsa spring-loaded plunger 26. The arm 24 is swung into contact with theloosely supported workpiece to a predetermined location where theabutment 22 accurately positions the surface it) which is to be ground,and the spring-urged plunger 26 may give way as it pivots the face 19against the abutment 22.

vilh the arm in the desired position, a gripping mechanism (notspecifically shown) such as an expanding collet 28 upon which theworkpiece has been pivotally positioned is operated to grip theworkpiece firmly in the exact position determined by the arm 24. Whenthe workpiece is thus gripped, the arm is retracted and the area 10 tobe ground is accurately located with respect to the edge of the table14. Two more indexing movements of the table bring the workpiece past anidle station 30 and to the grinding station 32, where the table issecurely clamped to hold the workpiece securely in a stationary positionfor the grinding operation. Upon completion of the grinding operationthe table may again be indexed to position the-finished workpiece at anunloading station 33.

The grinding wheel used by this invention is of the face grinding typewherein a plane side face 34 between an inner and outer diameter of acup-shaped wheel 36 is the working face. Such a wheel 36 may besupported by a spindle 38 driven by a pulley 40 through a belt (notshown) from a motor 42. The wheel, wheel spindle, and motor are mountedon a movable housing 44 which both slides and rotates on a horizontalpivot bar 46 (FIG. 1).

The pivot bar 46 is rigidly secured in the upper end 48 of a verticalpivot bar 50 rotatably mounted in a fixed housing 52 on the base 54. Anadditional strut support 56 extends between the lower end of the pivotbar 5i) and the outer end of the horizontal pivot bar 46. Oscillatorymotion of the upright pivot bar 50 about its axis swings-theworking faceof the grinding wheel 36 r 3,176,440 r a about the vertical line 12which is the center line or axis of the cylindrical surface to be groundas well as the center line of the pivot bar 50.

This motion is obtained by means of a double hydraulic motor'associatedwith houisng .52 and clearlyff shown in FIGURE 5. A gearSS keyed at 60to the pivot bar 50 meshes with opposed racks 62, formed integral withpistons 66, 68 which reciprocate in opposite. directions in parallelcylinders 70, 72, respectively, in the pivot bar housing 52. Pressurized'fluid'admitted to cylinder 70' through connection 74-serves to rotatepivot bar 50 in a counterclockwise direction in.FIGURE-5, as can beunderstood, and fluid admitted through aconnection 76 to cylinder 72will rotate the pivot bar 50 oppositely.

This oscillatory motion will, as. seen in FIGURE 3, rotate the workingface 34 of the off set grinding wheelthrough an are from the positiona't 34' shown-in dashed lines to the position shown in dash-dot lines at34" about the center line 12 to generate the cylindrical surface on theworkpiece W. During this arcuate motion, the working face ofthe wheel isalways tangent to the cylindrical sur-' face, and does not extendradially far enough to interfere a connection 112 acting on'theleft-handface of a piston 114 reciprocable in a cylinder 116 and to which theabut- 'ment member is attached: When it is desired to obtain afurther-than ordinary clockwise rotation of wheel head "44 for purposesof dressing" the, grinding wheel, fluid throughjafconnection117moyesvpiston 114 to the 'left,

' retracting abutment member 110' toallow a longer stroke of piston 86,The amount of retraction of abutment member 119 is governed by anotheradjustable stop memher 118 which limits the leftwardstroke of pistons 86and 114. r I

' The oscillating motion ofthe motors in the housing 1 44 which rotatethe grinding wheel about-fixed pivot bar is located 'on the dashedradial line 122" may be very working face 34 into contact'with theworkpiece.

with the enlarged cylindrical, central portion of the rocker armworkpiece held by the collet 28.

In addition to the arcuate motion about the centerline 12 the rotatinggrinding wheel of this invention partakes e of another motion during thegrinding operation which is in the plane of its working face, and maybe, for example, an arcuate motion about the horizontal pivot. bar 46.

This'exposes the entireieifective working face of the wheel to therelatively small surface to be ground, and is accomplished by a seconddouble acting fluid motor in the housing 44, as best seen in FIGURE, 6.p 7

As previously mentioned, the bar 46 is rigidly mounted at the upperportion 48 of the bar 50, and the housing 44 is rotatably mounted aboutthe horizontal bar. Fixedly secured to the horizontal bar 46, as shownin PIC-L6 is a gear 80 engaging opposed racks 82, 84 associated withpistons 86, 88 reciprocable respectively in parallel cylinders 90, 92.

The weight of the the righthand side of the bar 46 in FIGURE 6 tends tomove the housing 44 in a clockwise directionurging upper' piston 86 tothe left and lower piston 88'to the right in their respective cylinders.This tendency is counter 46 is schematically illustrated in FIGURE 4where the fullwidth of the face 34 'of'the grinding wheel 36 is visibleadjacent the endof the workpiece W upon which a cylindrical surface isto be ground. With the wheel in a starting position its center- 120 islocated on the solid radial line 122. .Motion in' a counterclockwisedirection about pivot bar; 46 to a position in' which the wheel center120' i .is accomplished within a'time equal to the time required forgenerating thecylindrical surface from position 34' to 34 in FIGURE 3.The position of the axis of bar 46,

s the trace of which'in FIG. {Us at the intersection of lines grindingwheel, spindle, and motor .on

122,122, is illustrative of-any linelying in a plane which plane isperpendicularto the line 12,.which latter is the center of thecylindrical surfaceto be ground. 7

Dressing apparatus 150 for the grinding wheel is fixedly located withrespect to the" horizontal pivot bar 46 and theupper portion 48 or thevertical pivot bar 50. During ordinarymass production grinding, thewheel may grind a large number of workpieces before dressing of thewheel is required. When dressing: is required, the'adjustable abutmentmember 110 isretracted by means of pressuracted to some extent by acounter balancing fluid spring mechanism 94' on the left-hand end of'thelower portion of the fluid motor. a The hydraulic counter balancingdevice comprises a relatively large piston 96'oontinu'ally' izing fluidthrough connection117, and the wheel is allowed to pivot clockwise untilits center reaches a point 152 (FIGURE 4) on the dash-double-dot radialline 154,

urged to the 'left end of a cylinder 98 by ipressurizedl fluid from asource R0, to be described, admitted 7 through a connection 100. The rod102 of piston 96 is secured by a bolt ,104 or other siutable means tothe;

smaller arealpiston' 88'to continually bias the housing 44 in acounterclockwise" direction about pivot bar 46.]

Motionin this direction is limited by an adjustable abutment means 106threaded in' the, left-handend of the cylinder 98. V 7

When it is desired to rotate" the housing 44- andits grinding wheel'34in a counterclockwise direction, the

biasing power of the mechanism 94 is amplified by, ad-j,

mitting fluid under pressure through a connection 108 to the uppercylinder to move piston86 to the right until the'lower piston assemblycontacts the abutment 106. 1 Clockwise motion of the housing .44, andwheel-36 about the pivotibar 46 is also limited byan adjustable abutmentmember 110 which halts the leftward. strokeofpiston 86.

For purposes .of dressing the'wheel'36,"in a manner later to bedescribed, the abutment member 110 may "be retracted to the left (to theposition shown, in phantom ment of Y the grinding wheel.

pressure of fluid from the source R0 admitted through outline) to allowmore, than the ordinary clockwise move- 7 i V The'abutment member 110 7is ordinarily held in .its normal, extended position by the v adistancesufiicient to traversethe face of the wheel across the point ofthe dressing tool. This method of dressing, often referred togasdiamond-sizing, is-a quick and extremely accurate manner of dressing astraight face on a wheel with a minimum of grit wastage.

Y Prior to each clockwise dip of the wheel for dressing purposes, thehousing 44 isadvanced longitudinally along the horizontal pivot barf46toward theworkpiece, preferably by an automatic, fluid motor actuated,ratchet fed 156 on theouter end of the'bar 46; f V

For the purpose of' operatin'g the" various operating lead screw deviceindicated schematically in FIG. 1 at 'means for the table, thegrinding-head, and the dressing operation inzthe" proper time';relationship, are two *mechanico-hydraulic programming units providedfor producing a cycle. of ,coordinatedmovement, illustrateddiagrammatically in FIGURE 7. "Each system may be constructed as aself-contained unithaving its own housing; not illustrated, which may bepositioned at any con-' 7 venient location on or adjacent the machineand connected to the various hydraulic cylinders by suitable flexiblepiping. One programming. unit powers and controls movement of thegrindingpwheel during the dressing operation, and the other or main unitcontrols the'loading, orienting, and-unloading of workpieces on thetable astwell as indexing motion of the table and the 'movement motor272 for engaging the brake.

of the grinding wheel during regular grinding operations. The two unitsoperate in turn under the control of a counting device.

The cam-driven liquid column type motion transfer unit 202 for dressingis shown in the upper left portion of FIGURE 7. It includes a primemover 2% driving a belt 266 which rotates a worm shaft 298. Shaft 208runs through a hydraulic clutch 210 and has mounted thereon worm 212 forrotating a cam shaft 214 by means of a Worm wheel 216. Fluid for thehydraulic clutch 210 is pumped from reservoir 220 by a pump 222 andthrough a spring loaded, solenoid actuated valve 224. When the valve isin its spring urged rest position (designated by the unhatched rectanglewith the single head flow-direction arrow), fluid will be allowed toflow back to the reservoir through line 218 from clutch 2317i), thusdisengaging the clutch and stopping cam shaft 214. When the valve 224 isin its solenoid actuated position (designated by the cross-hatchedrectangle with the double head flow direction arrow), pressurized fluidwill be allowed to flow from the pump 222 to the clutch 210, thusengaging the clutch and driving cam shaft 214.

Cam shaft 214 has two pulsator or transmitter sections each comprising arotary cam 226, the follower of which operates a piston 228 reciprocablein a cylinder 234). Each pulsator forms part of a liquid column typemotion transfer device which further includes a liquid column 232 and alow pressure reservoir 234. The operation of this system will be fullyapparent from the description of the main motivator unit 200, whichfollows.

The main mechanico-hydraulic drive unit 206 for driving the machinewhile grinding comprises a master camshaft 236, in the lower right ofFIGURE 7, carrying a plurality of cams 238 (only three shown), thefollowers of which operate the transmitter pistons 24 0, each of whichforms part of a liquid column type motion transfer device of which thereare three shown in the diagram of FIGURE 7. Each piston reciprocates ina cylinder 242 having a head 244 which contains a suitable inletreplenishing check valve 293 and a high pressure relief valve 295 bothof which communicate With a low pres- I sure oil reservoir 296preferably formed in a housing enclosing each drive unit.

For turning the camshaft 236, a motor 246 drives an input shaft 248 of atwo-speed transmission through a belt drive 250. The input shaft 248drives a pinion 252 and also the input member of ahydraulically-engaged, spring-released clutch 254. Pinion 252 drives agear 256 secured to a countershaft 258 which carries a pinion 260 at itsopposite end. Pinion 26f) drives a gear 262 and therewith constitutes aset of change speed gears. Gear 262 drives the input member of a secondhydraulicallyengaged, spring-released clutch 264. The driven members ofclutches 254 and 264 are secured to the opposite ends of a shaft 266,having a worm 268 thereon and a brake drum 27%. The latter has aspring-biased hydraulic Worm 268 drives a worm wheel 274 secured to themaster camshaft 236.

For the purpose of automatically controlling the start ing, stopping,and speed of the transmission, there is provided a hydraulic controlpump 2'76 driven from gear 262,- which may circulate a body of oilcontained in the housing surrounding the transmission. The pump 276 maydeliver to a combined accumulator and relief valve comprising a springloaded piston 27S and also supplies oil to a bank of control valves28%), 282 and 284. In the diagrams each valve is shown as a two-positionvalve, spring-biased to the normal position illustrated in which theconnections shown in the cross-hatched rectangles are established.Single-headed arrows are used to indicate flow at reservoir pressure anddouble-headed arrows to indicate flow at pump delivery pressure. Each ofthe valves, when shifted, establishes the connections shown in theunhatched rectangles immediately below the hatched rectangles.

Valve 280 is arranged to be shifted by a solenoid 286, which may alsoactuate an open-close dumping valve 287. Valves 282 and 284 are arrangedto be shifted by the adjustable cams 288 and 290, respectively, whichare positioned on camshaft 236. In addition, the valve 232 has ahydraulic holding cylinder 292 which holds the valve 282 in its shiftedposition until it is released by the shifting of valve 284. Valve 280 inthe position shown delivers pressure fluid to engage the brake 272 andalso exhausts fluid to release the low speed clutch 264. When shifted,valve 280 exhausts fluid to release brake 272 and supplies pressurefluid to engage the low speed clutch 264, subject, however, to aconjoint control by the valve 282.

The latter valve, in the position illustrated, exhausts fluid to releasethe high speed clutch 254 and places the low speed clutch 264 under thecontrol of valve 280. In its shifted position, valve 282, provided valve280 has been shifted, delivers pressure fluid to engage high speedclutch 254 and exhausts fluid to release low speed clutch 264-. Aspreviously explained, the valve 284 is merely a reset valve forbypassing the holding cylinder 292 to permit valve 282 to return to itsspring biased position.

Thus, energization of solenoid 236 will start the camshaft rotating atslow speed. Thereafter, the cam 288 will shift the transmission to drivethe camshaft at high speed, and still later the cam 290 will again shiftthe transmission to slow speed. So long as the solenoid 286 remainsenergized, the camshaft 236 Will continue to rotate, first at a slowspeed and then at a high speed during each revolution, controlling itsown speed changes by operation of the cams 238 and 290.

Tie camshaft 236 as previously mentioned drives a number of cam operatedhydraulic pulsator sections; Each section may comprise units duplicatingthe single acting pulsating cylinder 242, the head 244 of which containsthe replenishing check valve 293 and the spring closed relief valve 295.All the replenishing and relief valves are connected to a common oilreservoir 2% formed in the housing of the unit. The reservoir 2% ispreferably subjected to a low, super-atmospheric pressure by a body ofcompressed air or other pressure maintaining arrangements. Check valves293 allow flow from the reservoir 2% to the cylinder 242, while reliefvalves 295 allow flow oppositely when the cylinder pressure exceeds acertain value. Thus each of the pairs of valves 293 and 295 may bereferred to as a balancing valve and serve to balance the volume offluid in each of the liquid column sections, as will be later described.The pulsator sections are connected by closed liquid column lines 298with the two work performing motors for moving the grinding head.

In order to insure proper synchronization of the driving and drivenelements of each pulsator section, it is desirable to provide slightlymore fluid displacement in the driving or transmitting-elements 240-242than is present in their respective fluid motors at the opposite end ofthe liquid column line. Thus at the end of each advancing stroke of thetransmitter piston 246, a small amount of fluid will be discharged toreservoir 296 through its relief valve 295. This amount plus any amountlost by leakage will be returned to the liquid column at the end of thereturn stroke by the operation of the replenishing valve 293. I

In FIGURE 7 there are shown several circles marked R0 connected to theend of some of the motive cylinders opposite the liquid columnconnections. These symbols designate the return oil connections by meansof which a pulsator system may be hydraulically biased, as previouslymentioned, so as to maintain the follower in close contact with the camas the falling portion of the cam contour recedes from the follower.

The contours of the individual cams 226 and 238 are likewise notillustrated in specific detail since they may be formed in accordancewith the usual practice to cause the machine. Likewise the speed ratiobetween the high and low speeds of the cam shaft 236, and the durationof the high speed portion of the cycle, may be selected as desiredthrough use of the appropriate change gears 260-262 and through theadjustment of the cams 208 and 290, if desired. Of course, the two speedfeature of the transmission may be omitted andthe .high speed clutch254, the cams 288 and 290 andthe valves 28 2 and 284 eliminated.

. The units 202 and 200 for powering and controlling thedressingoperation and'the grinding mechanism, re-. spectively,areinterconnected by means of a known electrical counting device 300 forbeginning the dressing cycle immediately upon completion of the feedingof a predetermined number of workpieces and to stop the dressermotivator and commence .grindingthe instant the dressing operation iscomplete. The counter 300 contains: a conventional ratchet actuatingsolenoid, or count coil, 302 and a clutch reset solenoid, or clutchcoil, 304. In addition,.the counter contains a switch for making contactbetween connections 305 and306 while breaking contact betweenconnections 305 and 308'in one position, and vice-versa in the otherposition. Current for powering the circuitry of FIGURE 7 is provided bylines 310. I

When the main unit 200 is operating and workpieces are beingsuccessively ground by the wheel, a cam 312 closes contacts 314 once oneach revolution of cam shaft the outer diameter of the working'face'into contact with one edge of the cylindrical surfaceto be ground.At this instant the counterclockwise motion about the bar'46 is slowedby thecam and the transmission to a suitable speed, and arcuate motionofthe wheel about the center line 12 to generate the cylindrical surface'10 is commenced by cam moved liquidconnector 76. Both arcuatemotionsthen proceed simultaneously-the motion about vertical pivot bar50 generating the cylindrical contour and-the arcuate motion about, bar46 traversing the wheel across the work. vBoth arcuate motions areaccomplished with a controlled speed designed so that they are completedsimultaneously, afterwhich the grinding oper-' ationis completed and thewheelEis in the position indicated in solid lines in FIGURE 2. Thearcuate motion about the, center of bar 46 is illustrative of anysuitable traversing motion by which the flat face ofthe. wheel acrossthe surface being ground by the rotating I tio n shown in phantomoutline in FIGURE 2. The above operation is repeated by successiverevolutions of cam 236 at the end of a cycle. On each momentary closing2 shaft 236 until the wheel needs dressing, as determined by the counter300. I

-;Then, the main motivator camshaft 236'is stopped and the shaft 214 isrotated. First, the wheel is advanced by a liquid columnpulsator'section under control'of one its ordinary starting'fposition(120 to,152, FIGURE v4) are open and 306 areclosed, providing power forthe f solenoid 286 on valve 280, .287. When a preset number ofrevolutionsof cam shaft 236 (determined by the type of workpiece, etc.)have been recorded in'the counter,

the counter switch is thrownto the position in which contacts 305 and306are opened and 305 and 308 closed. The instant contacts 305 and: 306are opened, the brake 270, 272 isiappliedand the clutches 254 and ,264are'.

disengaged, thus stopping cam shaft 2 36.

Closing or contacts 305 and 30s closes solenoid sew-f.

' ated switch 320 for starting the pnme mover 204 of the a valve 224toenga'ge hydraulic clutch 210, permittingcam shaft 214 tobe-rotated byprime mover 204.; Thus imdresser drive unit, and also actuatessolenoidoperated mediately upon the'counter. recording a"pre'-setnumber.

in a clockwise direction about bar46 to traverse the diamond dressingapparatus. This is accomplished by backing off the limit stop v110by.moving piston. 114

. through liquid column'c'onnector 117 under control of the other ofthecarns 226; With 'the wheel satisfactorily dressed andgretumed to thenormal starting position, grinding operations are immediately resumed bystopping shaft 21 4 upon completion of its revolutionand resumingrotation ofcam shaft 236 the manner previously described. 1 7 While -theabove described embodiment 'constitutesa preferred mode of carrying outthis invention, many other formsmight be-adopted within the scope ofthe] actual of workpiece grinding cycles, that'mcchanism is idled 7 andthe dressing motivator is actuated to begin the dressn y l -x 7 When thedressing cycle has beencompleted, and

before cam shaft 214 has completed: its revolution, a

cam 322 'mornentarily closes contactsf324 and pulses current through thecounters clutch coil 304 which resets the counter and moves the countersswitch to break contact 8.13398 and again makecontacts 305 and :306'.,{As

current stops flowing through contacts 305 and 308, solenoid switch 320will shut off prime move'rj204andf the spring of valve 224 willreturn itto its-rest position disengaginghydraulic clutch; 210, thus allowingcamshaft 214 to quickly coast to astop, and the peaked'lobe Q to thesurface tobe ground, moving the-'wheel face rapidly of cam 322 to passjustbeyond thefollower. .Closingof Y contacts305 and 306 againgstartsthemain s5 by the. table invention-which isvariously claimedasr' 1'.The; method ofgrinding on'a workpiece a cylindrical surface about agivenaxis comprising the steps of rigidly locating the workpiece 'adjacentaface grinding wheel, continuously rotating the wheel about its axis,moving the wheel face into grinding contactv with the workpiece, andthen pivoting the axis of the wheel about the cylindrical axis'to'movethe wheel in an arcuate path about the'giyen cylindrical axis togenerate the cylindrical surface while simultaneously moving the wheelin the plane of its face'to expose an extendedi'area of thewheel face tothe workpiece.

the workpiece adjacent a face grinding wheel, "continu- .ously rotatingthe wheel about its axis with its'face tangent from a starting positioninto grinding contact with the workpiece, rnoving the wheel face. slowlyin an arcabout the given line to generate the cylindrical surface whilesimultaneously moving'the wheel 'face; in another are trolled by camactuated pulsator sections'on main shaft 1 1 236. Immediately, thegrinding wheel pivots rapidly for a short distance, under the influenceofa steep cam rise pulsing fluid' through liquid column 103, in acounter clockwise direction about the horizontal bar 46 to bring about'a line which remains in a plane which is normal to the given line ataspeedsufficient-to expose theentire effective width of the wheel faceto the workpiece during the time" required to generate the-surface, andrapidly j moving the wheel face back to thestarting position out ofcontact withthe workpiece. 7 I

3. Themethod ofgrinding a cylindrical surface about a given line on aworkpiececomprising the steps of fixing the workpiece adjacent a facegrinding wheel, continuously rotating the wheel about its axis, movingthe wheel face into grinding contact with the workpiece, moving thewheel in a first are about the given line to generate the cylindricalsurface while simultaneously moving the wheel in a second arc between astart and a finish position to expose the entire width of the wheel faceto the workpiece, repeating this operation on a preselected number ofworkpieces and then moving the wheel in the second are beyond the startposition and into contact with a fixedly positioned dressing tool tore-face the wheel.

4. In a grinding machine, apparatus for grinding a convex curved surfaceon a workpiece comprising gripping mechanism for securely clamping aworkpiece, a face grinding wheel rotating with its face tangent to thesurface to be ground, means for moving the wheel face along a first pathcorresponding to the surface to be ground and with the wheel facetangent to the surface, means for moving the wheel along a second pathin the plane of the wheel face and through a distance at least as greatas the effective width of the face to shift the point of grindingcontact across the face, and control apparatus connected to operate thetwo moving means together for grinding the surface utilizing an extendedarea of the wheel face.

5. In a grinding machine, apparatus for grinding a cylindrical surfaceabout a given line on a workpiece comprising gripping mechanism forfixedly locating a workpiece, a face grinding wheel rotating with itsface tangent to the cylindrical surface to be ground, means for movingthe Wheel in a first arc about the given line to generate thecylindrical surface, means for moving the wheel in a second are about aline which remains in a plane which is normal to the given line andthrough a distance greater than the effective width of the wheel face toshift the line of grinding contact across the face, and controlapparatus connected to cause the two moving means to operate togetherwhereby the rotating wheel grinds the cylindrical surface on a workpieceutilizing the full effective width of the wheel face.

6. In a grinding machine, apparatus for generating a cylindrical surfaceabout a given line comprising a grinding wheel rotating with its workingface tangent to the cylindrical surface to be generated, means formoving the wheel in an arcuate path about the given line to generate thecylindrical surface, means for moving the wheel in another path in whichthe wheel remains tangent to the cylindrical surface and moves through adistance greater than the effective width of the wheel face to shift thepoint of tangency across the face, and control apparatus for the twomoving means connected to operate them in overlapping timed sequencewhereby the rotating wheel undergoes motion tangent to the cylindricalsurface While generating the surface.

7. A dial type grinding machine comprising a base, a rotary index tablemounted for step-by-step rotation on the base, a plurality of workpieceholders mounted in equally spaced positions circumferentially of thetable, means for indexing the table in intermittent steps, a pluralityof operating stations on the base and distributed circumferentiallyaround the table including stations for loading, positioning, grindingand unloading workpieces successively, means at the grinding stationconnected to traverse a rotary grinding wheel across a workpieceperpendicularly to the axis of grinding wheel rotation and additionalcooperating means at the grinding station for simultaneously shiftingthe grinding wheel in an acrcuate path to grind an arcuate face on theworkpiece while utilizing an extended area of the wheel face.

8. A dial type grinding machine comprising a base, a

table mounted for rotary motion on the base, means connected to impartstep-by-step motion to the table, a plurality of workpiece holdersmounted in equally spaced positions circumferentially of the table, aplurality of operating stations on the base distributedcircumferentially around the table including stations comprising meansfor loading, means for positioning, means for grinding and means forunloading workpieces successively, the means at the grinding stationincluding apparatus connected to transverse a rotating grinding Wheelacross a workpiece in the plane in which the wheel rotates andadditional cooperating apparatus for simultaneously moving the grindingwheel in an arcuate path to generate a convex surface on a workpiece, aplurality of fluid motors connected to actuate all of the said means,and a mechanico-hydraulic motivator comprising a common camshaft and aplurality of rotary cam powered and controlled liquid column type motiontransfer devices connected to operate each of the fluid motors through acoordinated program of movements.

9. A grinding machine for grinding a curved ledge on a workpiece havinga raised portion adjacent the ledge and extending radially outward ofthe projected curved surface of the ledge comprising a base, a grindingwheel mounting having a first pivot about which the grinding wheel maybe oscillated to generate the curved surface and a second pivot aboutwhich the grinding wheel may be oscillated in a plane containing itsworking face, a wheel spindle having a face grinding wheel mounted forrotation about an axis parallel to a radius of the curved surface andbeyond the end of the first pivot, and means for mounting a workpieceopposite the wheel face and also beyond and in line with the first pivotwhereby a curved ledge surface may be ground without interference fromthe raised portion of the work.

10. In an automatic grinding machine, means for generating a smallcurved surface on a workpiece having a raised portion laterally adjacentand extending outwardly of the projected curved surface comprising abase, an index member mounted for step-by-step shifting motion on thebase, means on the member for carrying a plurality of workpieces duringgrinding operation, a loading station on the base including means forsupplying workpieces individually to the carrying means on the indexmember, an unloading station on the base including means for removingworkpieces individually from the carrying means on the index member, anda grinding station on the base including a rotary grinding wheel, meansconnected to shift the wheel along a first path in one direction togenerate a curved surface on a workpiece and means connected tosimultaneously shift the wheel along a second path in one direction toutilize an extended area of the wheel face on the surface, and controlmeans connected to operate the shifting means at the grinding stationsimultaneously with the supplying means and removing means at theloading and unloading stations and to shift the index membersimultaneously with shifting of the grinding wheel in the otherdirection along the first and second paths.

References Cited by the Examiner UNITED STATES PATENTS 2,544,604 3/51Mader 51-55 2,821,813 2/58 Degler 51-105 X 2,865,302 12/58 Amiet 512192,922,258 l/60 Bass 5155 J. SPENCER OVERHOLSER, Primary Examiner. JOHNC. CHRISTIE, Examiner.

1. THE METHOD OF GRINDING ON A WORKPIECE A CYLINDRICAL SURFACE ABOUT AGIVEN AXIS COMPRISING THE STEPS OF RIGIDLY LOCATING THE WORKPIECEADJACENT A FACE GRINDING WHEEL, CONTINUOUSLY ROTATING THE WHEEL ABOUTITS AXIS, MOVING THE WHEEL FACE INTO GRINDING CONTACT WITH THEWORKPIECE, AND THEN PIVOTING THE AXIS OF THE WHEEL ABOUT